Manufacture op tubes and pipes



June 2, 1931.

F. SNNICHSEN lET AL MANUFACTURE OF TUBES AND PIPES Filed Sept. 18. 1928 Patented June 2, 1931` FRANCIS sNNIoHsEN, FRANCIS AnoLr smsen, AANI) rrizru'irAN` ARTHUR NrconAYsEN,

or osLo, NoRwAY MANUFACTURR or vTurns AND Piras V I Application led September 18,1928, Serial No. 306,741, and in Norway August 11, 1928.

Our invention relates to the manufacture -of tubes and pipes and more particularly to the well known process of making these articles from a strip of metal in a continuous operation, first forming ya tubeblank by folding the strip longitudinally` by a suitablev rolling machine and thereupon welding' together by electrically generated heat along the so formed open seam the two adjacent edges of the metal. K

Various methods ,and devices have been proposed to carry out this welding process in a convenient and reliable manner, most of vwhich making use of electrodes in the form of rollers so disposedrelatively to the work-piece that the slit in the pipe to be A welded passes Ithe electric flux or the path iof the current between said electrodes at `right angles with the same. Devices have also been proposed in which path of the current is more o'r less in alignment with the seam.

Our invention relates to the latter class of devices and is limited to the use of electrodes sol disposed) relatively to the seam that the electric current path runs along the seam, parallel the same,the work-piece beinge for^the rest wholly outside of the electric flux 'or the current path. From this reason it is an important `point when carrying out our. invention to keep the piece of tubing under treatment by the electric current wholly'insulated (electrically) from n the feeding and pressing mechanism in operation in' close proximity to the seam or welding region. We have also found that it is of peculiar advantage to make use ofduction from the strongly heated seam.

This has proved to be of great importance diagrammatically how we prefer to carry out the invention, Figure l is a plan view and Figure 2 is a side elevation of the device. A is the tube blank, B, C and D, supporting feeding and pressure rollers, all of which areelectrically insulated. from their carriers and driving mechanisms; E, E and E2 are'electrodes in the form of rollers connected insuitable manner to a three-phase current system. Said rollers are adjustably mounted so that the distance between them can easily be varied. Preferably the distance between E and E is much greater than between E and E2. Preferably the roller electrode EL has a very narrow contact surface with the tube, the roller E a somewhat wider `and the rollerl E the widest. All of the rollers are in contact with both sides of the seam.v There may as will be understood'in this manner be established two 'electric current paths of diierent character. f At the point of contact of the roller E there will be an electric current of less intensity 'than at' the contact point of the roller E2 thereby obtaining a radually increasing heat along a considera le long part of the seam.

In the example described 3-phase current has been supposed to be used. In some cases a two-phase current may be used, especially by welding pipes of small diameter.

As will be understood from the foregoing the points at which current vis fed to the tube are according to the invention always and only lyin in the same line. The lon line or path o heating will result in asuiiiciently unlform heating of the whole pipe section 'to avoid undesirable contraction effects and to ensure an eective action of the roller press.

Claims.

1. Apparatus for welding by a continuous operation tube blanks formed out of a folded up strip of metal, comprising means to pass the tube blank, electrically insulated from the,feeding mechanism, into successive contact with a series of electrodes forming the'terminals of a poly-phase current system, said electrodes having a contact surface withthe tube blank covering both sides of the slit to be welded, the contact surface of successive electrodes being narrower lthan that of preceding electrodes. t

2.v An electric welding machine for tubes having a longitudinal slit, comprising a series of pairs of feed rollers, electrical' means for gradually heating in the direction of feed the abutting edges' of said slit from red heat between the first two pairs of said rollers to welding heat adjacent the last .pair of rollers in the series, said means inother in the direction of Vheat between the cluding a source of electric current and a circuit therefor, a plurality of terminals in the circuit positioned inv decreasing, spaced relation to each other in the direction of feed and in contact with said edges.

3. An electric welding machine for tubes having a longitudinal slit, comprising a.

series of pairs of feed rollers, yelectrical means for furnishing gradient steps of heating the abutting ed es of said slit from red rst two pairs of said rollers to welding heat adjacent the last pair white heat and pressing said edges tightly against eachother when at white heat proceeding in said direction, thereby causing them to formA a continuous, uninterrupted smooth weld. l l 6. A `process of seam-welding by the use of a multiple phase electric current, consistihg in feeding a workpiece in one direction of rollers in the series, said means including j a source of electric current and a circuit therefor, a plurality of terminals in the circuit in contact with both edges of said slit supplying' acontinuous flow of multiple phase current, said terminals'being positioned in decreasing, spaced relation to each feedand in contact with said edges. j 4

4. An electric welding machine for tubes having a longitudinal slit, comprising a series of pairs of feed rollers, electrical means for furnishing gradient steps of heating the abutting edges of said slit from red lheat`between the first two pairs of said rollers toA welding heat adjacentl the' last pair of' rollers in the series, said means including a source of electric current and a circuit therefor, a plurality of terminals in the circuit 'positioned in decreasing, spacedl relation to each other in the direction of feed and in contact with said edges, \said terminals straddling said slit, the preceding terminal being broader than the following terminal. l,

5. A process of electric seam-welding-consisting in feeding a .workpiece in onepdirection with the edges thereof to be welded in abutment, applyinggradient steps of electric heating to said edges from red. heat toV i 

